Conserving energy at home is in many ways a nuts-and-bolts activity, meaning that every little step counts. As a result, being informed about your many electronic devices, from stereos to computers to electric cooktops, is vital to informed energy efficiency. Determining roughly how much electricity is actually fairly easy.

The amount of watts that an electronic device uses is typically printed on the device itself, either stamped on the back or bottom, or printed on a nameplate. If you cannot find the wattage of a specific device you can figure it by multiplying the drawn current (amperes) by the voltage. Most U.S. appliances use 120 volts, although dryers, stoves, and other large appliances often use 240 volt outlets. The amount of amps should be stamped on the device as well. Otherwise an ammeter, a common electrician’s tool that can read the current running through a wire, must be used.

The Department of Energy offers an extensive list of typical wattages for home appliances. You’ll notice that nearly all of them have a range of wattages rather than one set number. That is because the amount of watts being drawn often depends on the device’s setting (i.e., volume controls on a stereo). Note that the nameplate wattage listed on the device is a maximum, so your stereo will actually use less watts unless you have it turned up all the way.

The water heater pretty much blows all others out of the water, hence the popularity and cost-effectiveness of solar water heaters. Others you might expect—the dishwasher, clothes dryer, and vacuum cleaner—all sap good amounts of electricity. There are some surprises, too. Take the hair dryer or the toaster oven, both using well over 1000 watts and nearly 2000 for the hair dryer. That is an awful lot of energy for such small devices.

Bear in mind that number of watts an appliances uses to run does not directly relate to how much money it costs or the percentage of your overall energy usage it makes up. You must factor in time of use. For instance, a vacuum cleaner can use over 1400 watts to run, but most people do not vacuum every day. In fact, most vacuum just once per week or less. Now compare that to the television, which only uses roughly 170 watts (for a large, projection TV), but the average person watches 6 hours of television per day.

When discussing which electronics use the most watts of electricity, it is also important to bear in mind “phantom loads,” or the amount of electricity a device draws even when it is switched off. However small individually, the phantom loads for all the appliances in the house can add up to a significant amount. The best way to avoid this issue is either to unplug a device when you are not using it or to plug multiple devices into a power strip and switch that to off when those devices are not being used. This works great for multi-component areas such as desktop computers and entertainment centers.